uu.seUppsala University Publications
Change search
Refine search result
1 - 42 of 42
Cite
Citation style
• apa
• ieee
• modern-language-association
• vancouver
• Other style
More styles
Language
• de-DE
• en-GB
• en-US
• fi-FI
• nn-NO
• nn-NB
• sv-SE
• Other locale
More languages
Output format
• html
• text
• asciidoc
• rtf
Rows per page
• 5
• 10
• 20
• 50
• 100
• 250
Sort
• Standard (Relevance)
• Author A-Ö
• Author Ö-A
• Title A-Ö
• Title Ö-A
• Publication type A-Ö
• Publication type Ö-A
• Issued (Oldest first)
• Created (Oldest first)
• Last updated (Oldest first)
• Disputation date (earliest first)
• Disputation date (latest first)
• Standard (Relevance)
• Author A-Ö
• Author Ö-A
• Title A-Ö
• Title Ö-A
• Publication type A-Ö
• Publication type Ö-A
• Issued (Oldest first)
• Created (Oldest first)
• Last updated (Oldest first)
• Disputation date (earliest first)
• Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
• 1.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
ESS RF Source and Spoke Cavity Test Plan2015Report (Other academic)

This report describes the test plan for the first high power RF source, ESS prototype double spoke cavity and ESS prototype cryomodule at the FREIA Laboratory.

• 2.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Precise measurements of hot S-parameters of superconducting cavities: Experimental setup and error analysisManuscript (preprint) (Other academic)

Superconducting accelerating cavities used in modern particle accelerators change their intrinsic properties when excited to very high field levels close to the critical field where the superconductivity is affected. In this report we describe a test-bench and data analysis procedure to determine the so-called hot S-parameters from strongly driven cavities and use them to quantify the properties of the cavity at varying field levels. The method is based on analysing reflection coefficient for a large number of configurations in a self-excited loop setup and determining the cavity coupling coefficient $\kappa=Q_0/Q_{ext}$ as a function of cavity voltage to high accuracy. Since $Q_{ext}$ is determined independently and is a constant, from the information of $\kappa$ the Q-slope can be determined.

• 3.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Minimization of power consumption during charging of superconducting accelerating cavities2015In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 801, p. 78-85Article in journal (Refereed)

The radio frequency cavities, used to accelerate charged particle beams, need to be charged to their nominal voltage after which the beam can be injected into them. The standard procedure for such cavity filling is to use a step charging profile. However, during initial stages of such a filling process a substantial amount of the total energy is wasted in reflection for superconducting cavities because of their extremely narrow bandwidth. The paper presents a novel strategy to charge cavities, which reduces total energy reflection. We use variational calculus to obtain analytical expression for the optimal charging profile. Enemies, reflected and required, and generator peak power are also compared between the charging schemes and practical aspects (saturation, efficiency and gain characteristics) of power sources (tetrodes, IOTs and solid state power amplifiers) are also considered and analysed. The paper presents a methodology to successfully identify the optimal charging scheme for different power sources to minimize total energy requirement.

• 4.
Natl Acad Sci Belarus, BI Stepanov Phys Inst, Minsk 220072, Byelarus..
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala Univ, Dept Phys & Astron, S-75120 Uppsala, Sweden.. Radboud Univ Nijmegen, Inst Mol & Mat, NL-6525 AJ Nijmegen, Netherlands.. Radboud Univ Nijmegen, Inst Mol & Mat, NL-6525 AJ Nijmegen, Netherlands.. Radboud Univ Nijmegen, Inst Mol & Mat, NL-6525 AJ Nijmegen, Netherlands.. Gothenburg Univ, Dept Phys, S-41296 Gothenburg, Sweden..
Multimode dynamics in a short-pulse THz free electron laser2014In: Physical Review Special Topics. Accelerators and Beams, ISSN 1098-4402, E-ISSN 1098-4402, Vol. 17, no 5, article id 050703Article in journal (Refereed)

The interaction of waveguide modes and consequences on laser operation are studied numerically in a THz free electron laser (FEL) driven by short electron bunches. The considered FEL cavity configuration is represented by a parallel-plate waveguide extending over the complete distance between cylindrical cavity mirrors with energy out-coupling through a rectangular slit in one of the mirrors. We describe the multimode FEL cavity desynchronization dynamics and predict strong enhancement in FEL power at special cavity configurations, when modes are degenerate. Furthermore, we predict that simultaneous excitation of several waveguide modes can occur but do not negatively influence the lasing process.

• 5.
B.I. Stepanov Institute of Physics, National Academy of Science of Belarus,.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. current address: Department of Physics, University of Gothenburg, Sweden .
Effects of emittance and energy spread in an electron bunch on THz radiation generated by a super-radiant source: report III of the series of reports by the Swedish FEL Center and FREIA Group2014Report (Other academic)

In this report we summarize our results on simulation of a super-radiant sourceoperating at the THz spectral range. We consider an open-type undulator com-prising plane magnets but without any guiding structure for generated THz eld.The undulator is assumed to be driven by electron bunches of femtosecond durationwhich are produced by an rf Linac. Using a numerical model developed, we analyzeeects of the bunch parameters on output performance of the super-radiant sourceand reveal some surprising results. Specically, we show that degradation in bunchspatial quality (increase in the bunch emittance) should lead to decrease in angulardivergence and spectral narrowing of the THz radiation. We also demonstrate thatelectron energy spread which commonly leads to bunch broadening and radiativeenergy drop can be eventually suppressed under appropriate conditions.

• 6.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Solid-state amplifier development at FREIA2014Conference paper (Refereed)
• 7.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Preliminary measurements of eight solid-statemodules of the 10 kW pulsed power amplifier at 352 MHz under development at FREIA2016Conference paper (Refereed)
• 8.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Wave Propagation Through a Waveguide Segment with Corrugated Walls: The Critical Role of the Corrugation Sharpness2013Conference paper (Other academic)
• 9.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
An approach to characterization of the Lorentz transfer function of ESS spoke cavities at FREIA2014Report (Other academic)
• 10.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Giant single-cycle THz pulsesfor pump-probe experiments2016Report (Other academic)

Strong-field single-cycle THz pulses are an invaluable tool forprobing and controlling low-energy excitations in matter such asmagnons, plasmons, phonons and Josephson waves. A novel scheme isproposed to generate quasi-half-cycle GV/m THz pulses with a mutlikilohertzrepetition rate. It makes use of coherent spontaneous emissionfrom a pre-bunched electron beam traversing an optimally taperedundulator. The scheme is the further development of the novel conceptof the slippage control in free-electron lasers [T. Tanaka, PRL 114 (2015)044801]. The pump-probe THz/X-ray/optical configuration is discussed.

• 11.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Quasi-half-cycle pulses of light from a tapered undulator2017In: PHYSICAL REVIEW ACCELERATORS AND BEAMS, ISSN 2469-9888, Vol. 20, no 8, article id 080703Article in journal (Refereed)

Strong-field few-cycle terahertz (THz) pulses are an invaluable tool for engineering highly non-equilibrium states of matter. A scheme is proposed to generate quasi-half-cycle GV/m-scale THz pulses with a multikilohertz repetition rate. It makes use of coherent spontaneous emission from a prebunched electron beam traversing an optimally tapered undulator. The scheme is the further development of the slippage control in free-electron lasers [T. Tanaka, Phys. Rev. Lett. 114, 044801 (2015)]. An explicit condition for the spectral amplitude of undulator radiation and a phase condition for the electron density distribution, required for the generation of desired pulses, are presented. The amplitude condition is met by proper undulator tapering, and a generic optimal undulator profile is found analytically. In order to meet the phase condition, the distance between the adjacent bunches is varied according to the instantaneous resonant undulator wavelength. A 3D analytical theory is complemented by a detailed numerical study based on a direct solution to the 3D wave equation.

• 12.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
A Method for High-Precision Characterization of the Q-Slope of Superconducting RF Cavities2016In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 64, no 11, p. 3764-3771Article in journal (Refereed)

We propose a novel method for high-precision determination of a quality factor Q(0) of a superconducting radio-frequency cavity as a function of the strength of the field excited in the cavity, the so-called Q-slope. Usually, the cavity parameters are measured only at resonance for different cavity field strengths, but such a single data point measurement for a given field strength results in a 10%-15% uncertainty in Q(0). In contrast, we propose a method that improves the accuracy of Q(0) determination by an order of magnitude. We vary the phase of an excited stabilized field in the cavity and measure the reflection coefficient of the cavity as a function of the phase. The procedure is repeated for different strengths of the excited field. Given the fact that the complex reflection coefficient of a cavity describes a perfect circle in polar coordinates as a function of the field phase for a constant field strength, we find the coupling coefficient much more accurately by fitting the overdetermined set of measured data to the circle for each value of the cavity field. From the time-decay measurement, which allows least-squares minimization, we accurately find the total (loaded) quality factor and deduce Q(0) with an uncertainty of around 1%.

• 13.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
A megawatt class compact power combiner for solid-state amplifiers2014In: Journal Electromagnetic Waves and Applications, ISSN 0920-5071, E-ISSN 1569-3937, Vol. 28, no 18, p. 2243-2255Article in journal (Refereed)

We propose a compact multiport two-stage combiner capable of handling peak power up to 10MW at the UHF band and suitable for particle accelerator applications. The detailed electromagnetic and thermal simulations of the combiner operating at the ESS specifications of 400kW at 352MHz are presented. At the first stage, the power is combined to a 100kW level by means of a non-resonant 12-way radial combiner, which is assumed to be fed by 8kW solid-state amplifiers. At the second stage, a waveguide combiner with T-shape couplers separated by a half-wavelength of the fundamental waveguide mode is used in order to bring the combined power to the required level. The combiner is broadband and has a relative power non-uniformity less than 5% over a 10MHz frequency band around the central frequency. The size of the proposed combiner is several times smaller than the existing ones. We also present low-power measurement results of a prototype of the radial combiner.

• 14.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Proposal for Design and Test of a 352 MHz Spoke RF Source2012Report (Other academic)

More than a dozen of spoke resonators prototypes (SSR, DSR, TSR) have been constructed and tested worldwide. None have accelerated beam until now and the ESS LINAC will be the first accelerator to operate with spoke cavities. Experience with other types of superconducting cavities indicates that high-power test is vital for reliable operation of the cavity in an accelerator. Although characteristics of a bare cavity can be obtained in a low-power test some important features of a `dressed' cavity like the electroacoustic stability and tuning system can be studied only in a high-power test stand. The ESS LINAC is a pulsed machine and the Lorentz detuning originating from the electromagnetic pressure on the cavity walls is expected to be strong. The Lorentz force along with the cavity sensitivity to mechanical excitations at some resonant frequencies may lead to self-sustained mechanical vibrations which make cavity operation dicult. Practical experience shows that increasing the boundary stiness will decrease the static Lorentz force detuning but not necessarily the dynamic one. Therefore, the FREIA group at Uppsala University is building a high-power test stand able to study performance of the ESS spoke cavity at high power. The RF test stand will be able to drive the cavity not only in the self-excitation mode but also with closed RF loop and fixed frequency. The later technique will be used to reproduce the shape of the cavity voltage pulse as it is expected to be in the cavity operating in the ESS LINAC such that the cavity tuning compensation system will be tested under realistic conditions.

• 15.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala Univ, Dept Phys & Astron, S-75120 Uppsala, Sweden..
12-Way 100 kW Reentrant Cavity-Based Power Combiner With Doorknob Couplers2018In: IEEE Microwave and Wireless Components Letters, ISSN 1531-1309, E-ISSN 1558-1764, Vol. 28, no 2, p. 111-113Article in journal (Refereed)

We present radio frequency (RF) and thermal characterization of a compact 12-way power combiner designed for operation at 352 MHz at a power level of 100 kW with 5% duty factor. The combiner is based on a reentrant cavity with 12 input doorknob couplers and one output coupler that is integrated with the post of the cavity and forms doorknob type geometry. We introduce convenient design formulas that allow easy identification of a suitable parameter space, which is then refined with numerical simulations. Low-power RF measurements of a prototype show 0.2% insertion loss and a relative rms amplitude imbalance between the ports of 0.1% and phase imbalance of 0.036 degrees rms. The matching is better than -25 dB over a 3-dB bandwidth around the design frequency. We also tested the combiner up to 200 kW and found the RF loss to be comparable to that of the low-power measurement. In a long test run at 100 kW with 5% duty factor, the combiner temperature stabilized at 10 degrees above ambient.

• 16.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
The sharpness-induced mode stopping and spectrum rarefication in waveguides with periodically corrugated walls2013In: Waves in Random and Complex Media, ISSN 1745-5030, E-ISSN 1745-5049, Vol. 23, no 2, p. 89-113Article in journal (Refereed)

Starting from the rigorous excitation equation, the propagation of waves through a 2D waveguide with the periodically corrugated finite-length insert is examined in detail. The corrugation profile is chosen to obey the property that its amplitude is small as compared to the waveguide width, whereas the sharpness of the asperities is arbitrarily large. With the aid of the method of mode separation, which was developed earlier for inhomogeneous-in-bulk waveguide systems [Waves Random Media 2000; 10: 395], the corrugated segment of the waveguide is shown to serve as the effective scattering barrier whose width is coincident with the length of the insert and the average height is controlled by the sharpness of boundary asperities. Due to this barrier, the mode spectrum of the waveguide can be substantially rarefied and adjusted so as to reduce the number of extended modes to the value arbitrarily less than that in the absence of corrugation (up to zero), without changing considerably the waveguide average width.

• 17.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. current address: Department of Physics, University of Gothenburg, Sweden .
Conceptual Design of an Stockholm-Uppsala THz FEL Oscillator: report I of the series of reports by the Swedish FEL Center2013Report (Other academic)

The Stockholm-Uppsala FEL center is currently studying the user interest in terahertz radiation in the M\"{a}laren region and considering the possibility of building a terahertz free-electron laser (THz FEL) in the FREIA laboratory. In this memo we present the design of an electron RF linac required to drive a superradiant THz source.

• 18.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Self-amplified coherent spontaneous emission in a free electron laser with "quiet" bunches2013In: Physical Review Special Topics. Accelerators and Beams, ISSN 1098-4402, E-ISSN 1098-4402, Vol. 16, no 3, p. 030702-Article in journal (Refereed)

For a planar free electron laser (FEL) configuration we study self-amplified coherent spontaneous emission driven by a gradient of the bunch current in the presence of different levels of noise in bunches. The longitudinal granularity of the electron bunch density originating from shot noise is maintained throughout the analysis. For the FEL model with the SwissFEL injector bunch parameters, we calculate the probability density distribution of the maximum power of the radiation pulses for different levels of shot noise. It turns out that the temporal coherence quickly increases as the noise level reduces. We also show that the FEL based on coherent spontaneous emission produces almost Fourier transform limited pulses. The analysis indicates that the time-bandwidth product is mainly determined by the bunch length and the interaction distance in an undulator. Calculations of the FEL characteristics for different rise times of the front of the current pulse are performed, and it is found that a reduced level of the power fluctuations is preserved for the bunch current pulse with a front duration up to several FEL wavelengths. We also propose a novel scheme that permits the formation of electron bunches with a reduced level of noise and a high gradient of the current at the bunch tail to enhance coherent spontaneous emission. The presented scheme uses effects of noise reduction and controlled microbunching instability and consists of a laser heater, a bunch compressor, and a shot noise suppression section. We show that shot noise reduction by 2 orders of magnitude in electron bunches produced by the SwissFEL injector can be achieved in a compact noise suppression section. The noise factor and microbunching gain of the overall proposed scheme with and without laser heater are estimated.

• 19.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, The Svedberg Laboratory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
RF Power Consumption in the ESS Spoke LINAC: ESS TDR Contribution2013Report (Other academic)

• 20.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Calibration procedure for RF test2016Report (Other academic)

Precision measurements of quality factors of superconducting resonators are desired in the determination of ESS superconducting cavities. Components of the measurement setup, such as interconnecting cables and adapters, introduce variations in magnitude and phase that can mask the actual response of the device under test. In order to have an accurate measurement, calibration becomes the first and most important step. FREIA has developed a test stand based on a self-exited loop for demonstrating the performance of superconducting cavities at low power level. So far, a single spoke cavity Hélène and a double spoke cavity Germaine from IPNO have undergone a cold test with FREIA SEL. Several calibration procedures are studied in these tests. Similar test results as IPNO's previous test were obtained with the FREIA system, which means the accuracy control fulfills the requirements.

This report presents the calibration procedure of the FREIA SEL test.

• 21.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
Time Domain Characterization of High Power Solid State Amplifiers for the Next Generation Linear Accelerators2018In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 60, no 1, p. 163-171Article in journal (Refereed)

This paper presents the time domain characterization of high power pulsed solid state amplifiers to be used forlinear accelerator applications. The study comprises nonlinear circuit envelope simulations and time domainenvelope measurements. Measurements and simulations are performed under the pulsed conditions (3.5 mspulse width, 5% duty cycle) specific to the European Spallation Source (ESS) high intensity proton accelerator.We measure the characteristics of pulsed LDMOS based power amplifiers such as: pulse droop along the pulse,efficiency, average envelope pulse amplitude and phase, pulse drain current waveform, pulse drain voltagewaveform, etc. A comparison between the measured results and the simulated results is also presented. Inaddition to the pulse profile characterization, the pulse to pulse (P2P) stability of the presented solid state poweramplifier (SSPA) is investigated as variations of amplitude and phase. The P2P stability simulations areintroduced as a combination of the Monte-Carlo simulations and the nonlinear circuit envelope simulations. Thesimulated results are used for fitting the P2P measurements to give an early insight of causes of instabilities ofthe nonlinear LDMOS models.

• 22.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. FREIA.
Time domain characterization of high power RFpulsed solid state amplifiers for linear accelerators2016Conference paper (Refereed)
• 23.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
RF Test of the ESS Double Spoke Cavity2016Report (Other academic)

A bare spoke cavity has been tested at FREIA Laboratory with a Self-exited loop at low power level to confirm its vertical test performance at IPNO. Similar test results as IPNO's previous test were obtained with FREIA system. This report presents the details of each measurement.

• 24.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Test Characterization Of Superconducting Spoke Cavities At Uppsala University2015Conference paper (Refereed)

As part of the development of the ESS spoke linac, the FREIA Laboratory at Uppsala University, Sweden, hasbeen equipped with a superconducting cavity test facility. The cryogenic tests of a single and double spoke cavitydeveloped by IPN Orsay have been performed in the new HNOSS horizontal cryostat system. The cavities areequipped with a low power input antenna and a pick-up antenna. Different measurement methods wereinvestigated to measure the RF signal coupling from thecavity. Results from the tests confirm the possibility to transport the cavities from France to Sweden without consequences. We present the methods and preliminary study results of the cavity performance.

• 25.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. IPN Orsay, France. IPN Orsay, France.
RF test of ESS superconducting spoke cavities at Uppsala University2016In: Proceedings of  IPAC2016, 2016, p. 791-794Conference paper (Other academic)

The European Spallation Source (ESS) is an accelerator-driven neutron spallation source built in Sweden. It will deliver the first protons to a rotating tungsten target by 2019 and will reach the full 5 MW average beam power in the following years. The superconducting Spoke cavities are considered compact structures at low frequencies and having an excellent RF performance in both low and medium velocity regimes, therefore ESS will include a total of 26 double-spoke cavities. The testing of the double-spoke prototype cavity at high power has been conceded to Uppsala University, Sweden, where the Facility for Research Instrumentation and Accelerator development (FREIA) has been equipped with superconducting cavity test facility.

A bare spoke cavity has been tested at the FREIA Laboratory with a self-exited loop at low power level to confirm its vertical test performance at IPNO. Similar test results as IPNO's previous test were obtained with FREIA system. In this paper we present the methods and preliminary study results of the cavity performance.

• 26.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
RF Test of the Hélène Single Spoke Cavity2015Report (Other academic)

FREIA has developed a test stand based on a self-exited loop for demonstrating the performance of superconducting cavities at low power level. Before the arrival ESS double spoke cavities, a single spoke cavity Hélène from IPNO has undergone a cold test with FREIA SEL to check our test method, hardware set-up and cryo-system, etc. Similar test results as IPNO's previous test were obtained with the FREIA system. This report presents the details of the FREIA SEL setup and each measurement.

• 27.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Characterization of a beta=0.5 double spoke cavity with a fixed power coupler2019In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 927, p. 63-69Article in journal (Refereed)

ESS, the European Spallation Source, will adopt a single family of double spoke cavities for accelerating the beam from the normal conducting section to the first family of the elliptical superconducting cavities. It will be the first double spoke cavities in the world to be commissioned for a high power proton accelerator. The first double spoke cavity for the ESS project was tested with high power in the HNOSS cryostat at Uppsala University. A pulse-mode test stand based on a self-excited loop was used in this test. The qualification of the cavity package involves a double-spoke superconducting cavity, a fixed fundamental power coupler, tuner, a low-level radiofrequency (LLRF) system and a high-power radiofrequency (RF) station. The test represents an important verification milestone before the module assembly. This cavity had unfortunately a high dynamic loss of 12W @ 9 MV/m, where potential causes for such a high value have been studied and corresponding suggestions are listed. This paper presents the test configuration, RF conditioning history, first high power performance and experience of this cavity package.

• 28.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
First High Power Test of the ESS Double Spoke Cavity2017Report (Other academic)

The first double spoke cavity for ESS project was tested with high power in the HNOSS cryostat at FREIA Laboratory. This cavity is designed for 325.21MHz, a pulse mode with 14 Hz repetition rate, up to peak power of 360 kW. The qualification of the cavity package in a high power test, involved a spoke superconducting cavity, a fundamental power coupler, LLRF system and a RF station, represented an important verification before the module assembly. This report presents the test configuration, RF conditioning history and first high power performance of this cavity package.

• 29.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Compact undulator line for a high-brilliance soft-X-ray free-electron laser at MAX IV2019In: Journal of Synchrotron Radiation, ISSN 0909-0495, E-ISSN 1600-5775, Vol. 26, p. 891-898Article in journal (Refereed)

The optimal parameter space for an X-ray free-electron laser (FEL) in the self-amplified spontaneous emission (SASE) operation mode is examined. This study focuses on FEL operation with a shorter undulator period and higher undulator strength made available through recent developments in in-vacuum, cryogenic and superconducting undulators. Progress on short-period undulator technologies is surveyed and FEL output characteristics versus undulator parameters are computed. The study is performed on a case of the planned soft-X-ray FEL at the MAX IV Laboratory in Sweden. An extension of the SASE mode into the harmonic lasing self-seeded mode is also analysed.

• 30.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Undulator Considerations in the Baseline Design of the MAX IV Soft X-Ray Laser2018Report (Other academic)

We examine the optimal parameter space for an x-ray free-electron laser (FEL) in the operation mode of self-amplified spontaneous emission (SASE). The study focuses on FEL operation with a shorter undulator period and higher undulator strength made available through recent developments in in-vacuum, cryogenic and superconducting undulators. We survey the progress on short-period undulator technologies and compute the FEL output characteristics versus the undulator parameters. We perform the study on a case of the planned soft-x-ray FEL at the MAX IV Laboratory in Sweden. An extension of the SASE mode into the harmonic lasing self-seeded mode is also analysed.

• 31.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. STFC Daresbury Laboratory, Warrington, United Kingdom.
Science Requirements and Performance Specification forthe CompactLight X-Ray Free-Electron Laser2019Report (Other academic)

CompactLight is a consortium funded by the European Union through the Horizon 2020 Research and Innovation Programme under Grant Agreement No. 777431.  This report summarizes science requirements and performance specification for the CompactLight x-ray free-electron laser.

• 32.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Stockholm Univ, Stockholm, Sweden. Cockcroft Inst, Warrington, Cheshire, England;STFC Daresbury Lab, Warrington, Cheshire, England. Univ Pecs, Pecs, Hungary. SPring 8 Ctr, RIKEN, Kobe, Hyogo, Japan. SPring 8 Ctr, RIKEN, Kobe, Hyogo, Japan. Cockcroft Inst, Warrington, Cheshire, England;Univ Strathclyde, Dept Phys, SUPA, Glasgow, Lanark, Scotland. SPring 8 Ctr, RIKEN, Kobe, Hyogo, Japan. Cockcroft Inst, Warrington, Cheshire, England;STFC Daresbury Lab, Warrington, Cheshire, England. Univ Pecs, Pecs, Hungary. Univ Pecs, Pecs, Hungary. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Attosecond single-cycle undulator light: a review2019In: Reports on progress in physics (Print), ISSN 0034-4885, E-ISSN 1361-6633, Vol. 82, no 2, article id 025901Article, review/survey (Refereed)

Research at modern light sources continues to improve our knowledge of the natural world, from the subtle workings of life to matter under extreme conditions. Free-electron lasers, for instance, have enabled the characterization of biomolecular structures with sub-angstrom spatial resolution, and paved the way to controlling the molecular functions. On the other hand, attosecond temporal resolution is necessary to broaden our scope of the ultrafast world. Here we discuss attosecond pulse generation beyond present capabilities. Furthermore, we review three recently proposed methods of generating attosecond x-ray pulses. These novel methods exploit the coherent radiation of microbunched electrons in undulators and the tailoring of the emitted wavefronts. The computed pulse energy outperforms pre-existing technologies by three orders of magnitude. Specifically, our simulations of the proposed Soft X-ray Laser at MAX IV (Lund, Sweden) show that a pulse duration of 50-100 as and a pulse energy up to 5 mu J is feasible with the novel methods. In addition, the methods feature pulse shape control, enable the incorporation of orbital angular momentum, and can be used in combination with modern compact free-electron laser setups.

• 33.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. European Spallation Source.
PROGRESS AT THE FREIA LABORATORY2015In: Proceedings of IPAC'15, JACoW: The Joint Accelerator Conferences Website , 2015Conference paper (Refereed)

The FREIA Facility for Research Instrumentation and Accelerator Development at Uppsala University, Sweden, has reached the stage where the testing of superconducting cavities for the European Spallation Source (ESS) is starting. The new helium liquefaction plant has been commissioned and now supplies a custom-made, versatile horizontal cryostat, HNOSS, with liquid helium at up to 140 l/h. The cryostat has been designed and built to house up to two accelerating cavities, or, later on, other superconducting equipment such as magnets or crab cavities. A prototype cavity for the spoke section of the ESS linac will arrive mid 2015 for high-power testing in the horizontal cryostat. Two tetrode-based commercial RF power stations will deliver 400 kW peak power each, at 352 MHz, to the cavity through an RF distribution line developed at FREIA. In addition, significant progress has been made with in-house development of solid state amplifier modules and powercombiners for future use in particle accelerators. We report here on these and other ongoing activities at the FREIA laboratory.

• 34.
Natl Sci Ctr, Kharkov Inst Phys & Technol, Kharkov, Ukraine.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Multislice Model Of Electron Bunch For Study Of Ballistic Bunching Of Low Emittance Beams2018In: Problems Of Atomic Science And Technology, ISSN 1562-6016, no 3, p. 73-80Article in journal (Refereed)

At ballistic bunching of an electron beam the transverse distribution of space-charge field varies along a bunch greatly. It can lead to emittance growth unless to provide its compensation. To study this problem, a multislice model of a bunch of relativistic charged particles that needs no smallness of energy spread between slices are developed. This removes the limit on the value of the RF field that modulates the slices by velocity before their injection into a drift space. The longitudinal dynamics of each slice is determined by its interaction with the field of the entire bunch averaged over the slice. Transverse beam characteristics are found from a differential equation for root-mean-square envelope of a beam.

• 35.
NSC KIPT, Acad Skay 1, UA-61108 Kharkov, Ukraine.
NSC KIPT, Acad Skay 1, UA-61108 Kharkov, Ukraine. Univ Gothenburg, Kemivagen 9, S-41296 Gothenburg, Sweden. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Design study of a low-emittance high-repetition rate thermionic rf gun2017In: PHYSICAL REVIEW ACCELERATORS AND BEAMS, ISSN 2469-9888, Vol. 20, no 5, article id 053401Article in journal (Refereed)

We propose a novel gridless continuous-wave radiofrequency (rf) thermionic gun capable of generating nC ns electron bunches with a rms normalized slice emittance close to the thermal level of 0.3 mm mrad. In order to gate the electron emission, an externally heated thermionic cathode is installed into a stripline-loop conductor. Two high-voltage pulses propagating towards each other in the stripline-loop overlap in the cathode region and create a quasielectrostatic field gating the electron emission. The repetition rate of pulses is variable and can reach up to one MHz with modern solid-state pulsers. The stripline attached to a rf gun cavity wall has with the wall a common aperture that allows the electrons to be injected into the rf cavity for further acceleration. Thanks to this innovative gridless design, simulations suggest that the bunch emittance is approximately at the thermal level after the bunch injection into the cavity provided that the geometry of the cathode and aperture are properly designed. Specifically, a concave cathode is adopted to imprint an.-shaped distribution onto the beam transverse phase-space to compensate for an S-shaped beam distribution created by the spherical aberration of the aperture-cavity region. In order to compensate for the energy spread caused by rf fields of the rf gun cavity, a 3rd harmonic cavity is used. A detailed study of the electrodynamics of the stripline and rf gun cavity as well as the beam optics and bunch dynamics are presented.

• 36.
National Science Center "Kharkiv Institute of Physics and Technology", Kharkiv, Ukraine.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. current address: Department of Physics, University of Gothenburg, Sweden . Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Design of a Superconducting Linear RF Accelerator for a Superradiant THz FEL: report II of the series of reports by the Swedish FEL Center and the FREIA Group2013Report (Other academic)

The Stockholm-Uppsala FEL center is currently studying the user interest in terahertz radiation in the M\"{a}laren region and considering the possibility of building a terahertz free-electron laser (THz FEL) in the FREIA laboratory. In this memo we present the design of an electron superconducting RF linear accelerator required to drive a superradiant THz source.

• 37.
National Science Center "Kharkiv Institute of Physics and Technology", Kharkiv, Ukraine.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. current address: Department of Physics, University of Gothenburg, Sweden . Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Towards a combined THz/X-ray source: report IV of the series of reports by the Swedish FEL Center and the FREIA Group2014Report (Other academic)

In the framework of development of a Free Electron Laser (FEL) by the Swedish FEL Center and theFREIA laboratory, we discuss the design of a versatile combined THz/X-ray source driven by high-brightness electron bunches produced by a superconducting linear accelerator. The ultimate goal isto build a versatile photon source for multidisciplinary research at the FREIA laboratory of UppsalaUniversity. A signicant part of equipment is potentially available via the FREIA project at UppsalaUniversity after 2018 such as the cryogenic system, the system of power generation and transportation,control and data acquisition systems. For pump-probe experiments, we discus a possibility to combinethe THz source with an X-ray source based on the inverse Compton scattering of quantum laser pulsesfrom electron bunches. The X-ray source will operate in the \water window" with an output intensitycomparable to a second generation synchrotron. The envisioned THz/X-ray source is compact andcomparable in budget to the cost of one beamline at MAX IV. The source can also be used to trainstudents in accelerator physics and applications of THz and synchrotron radiation.

• 38.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Cryogenic Synopsis from the Testing of the Fully Equipped ESS’ Double Spoke Cavity Romea2017Report (Other academic)
• 39.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Child-Langmuir law for photoinjectors2018In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 113, no 20, article id 204103Article in journal (Refereed)

The space-charge field at the cathode limits the current density extracted from particle sources such as photoinjectors. For a long time, the maximum current has been estimated by using the classical Child-Langmuir law, which is derived with an assumption inconsistent with the conditions of modern laser-driven electron guns. Here, we introduce a theoretical model that accurately accounts for space-charge effects in transversely confined particle beams emerging from photocathodes. The model enables us to (i) determine the maximum current density extractable from the photocathode for an arbitrary cathode radius, (ii) reveal its dependence on the transverse profile of the particle beam, and (iii) predict its upper limit for structured beams such as the ones produced by surface-plasmon resonance-enhanced photocathodes.

• 40.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
Analytical model of waveform-controlled single-cycle light pulses from an undulator2018In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 43, no 4, p. 819-822Article in journal (Refereed)

This Letter builds upon a recent concept [Phys. Rev. Lett. 113, 104801 (2014)] for producing ultrashort optical pulses through the coherent radiation of electrons in an undulator. Each pulse contains only a single oscillation cycle, and has a controlled waveform (and hence a stable carrier-envelope phase). While the concept had been demonstrated numerically, this Letter provides an analytical model for the radiation mechanism, thereby revealing three key observations: (i) the correlation between the waveforms of the optical and undulator fields; (ii) the free-space dispersion of transversely confined light; and (iii) the dependence of the optical pulse shape on the undulator field strength.

• 41.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, The Svedberg Laboratory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, The Svedberg Laboratory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, The Svedberg Laboratory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. CERN, Geneve, Schweiz.
Uppsala high power test stand for ESS spoke cavities2012In: Proceedings of LINAC2012, 2012, p. 711-713Conference paper (Refereed)
• 42.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Selection of RF Power Source and Distribution Scheme at 352 MHz for Spoke Cavities at ESS and FREIA2012Report (Other academic)

The report describes selection of RF power source and distribution scheme for spoke cavities at ESS and FREIA.  The European Spallation Source (ESS) is the world’s most powerful neutron source, which contain 36 superconducting spoke cavities at 352MHz and provide power of 0.5MW to the beam. The baseline for the RF system is a point-to-point generation and distribution  from a single source to a single accelerating cavity.The RF system that has to generate this power and distribute it to the accelerating cavities, is a main resource driver for linear accelerators in form of investment, operation and maintenance. Therefore the technical alternatives are compared to minimize capital and running cost of the accelerator, without compromising its reliability. At 352 MHz and 350 kW RF power output, tetrode amplifiers are selected because of their advantages of being cheap, reliable, simple and efficient as compared to the other RF power amplifiers. The tetrodes, due to their low gain, need a pre-driver. The solid state amplifier technology is selected as a pre-driver due to its simplicity, reliability and efficiency. Half height aluminum WR2300 wave guides shall be used for RF distribution. This solution makes it possible to discard the circulator from the RF distribution chain, thus improving system efficiency.

1 - 42 of 42
Cite
Citation style
• apa
• ieee
• modern-language-association
• vancouver
• Other style
More styles
Language
• de-DE
• en-GB
• en-US
• fi-FI
• nn-NO
• nn-NB
• sv-SE
• Other locale
More languages
Output format
• html
• text
• asciidoc
• rtf